1. Technical Field
The present invention relates generally to the electroplating on plastic process, system and components thereof including plastic parts which are electroplated. More particularly, the present invention relates to electroplating racks and plastic parts configured for mounting thereon whereby the racks substantially reduce or eliminate the use of clips and reduce the time required for loading and unloading the plastic pieces from the rack.
2. Background Information
Electroplating is a plating process that uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal. Electroplating is primarily used for depositing a layer of material to bestow a desired property (for example, abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc.) to a surface that otherwise lacks that property.
The process used in electroplating is called electrodeposition. It is analogous to a galvanic cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that comprise it and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they “plate out” onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated, vis-a-vis the current flowing through the circuit. In this manner, the ions in the electrolyte bath are continuously replenished by the anode.
Plastic parts can be plated with many finishes such as nickel, chrome or other metals. The raw plastic part is attached to a metal rack that is immersed into various tanks. In some of these tanks, the racks are supplied with electric current. The rack with the plastic parts go into an acid bath that chemically etches the surface of the part. After various cleaning tanks, the rack goes into a bath with a suspension of copper that attaches to the rough surfaces—this process is called deposition. Once enough copper is on the part surface and the rack clips are in electrical connection with the part surface, the part is electrically conductive and the rack can go into the electrodeposition tanks and receive the final metallic coating or coatings of nickel, chrome or other metals.
Most high volume applications use dedicated plating racks which in today's market can cost well over $1000 each and last only 1000 cycles before needing to be replaced or rebuilt. Once welded together with all the clips in the correct locations, the rack is immersed in a plastic material such as Plastisol to coat the part of the rack that will be immersed in the tanks. The plastic material around the clip jaws is mechanically removed so that the end of the clip is exposed, conductive and can mechanically grab the part.
For large parts sold at relatively higher prices, manually loading and unloading the racks is a small aspect of the overall part cost, but for small parts, one of the larger costs involved is the manual loading and unloading. In addition, the longer it takes for loading and unloading, the more racks will be needed to keep up with the processing speed of the plating system.